Chapter 5 - Roots And Soils Flashcards
Region of cell division
*Apical meristem. Primary growth in length.
Root cap
- “Helmet” for the root.
- Function: protection to the root while it grows and pushes through abrasive soil. Produces a mucus for lubrication. Controls direction of growth (sensitive to gravity).
Protoderm
A
Ground meristem
A
Region of elongation
- “Kid” stage (growing bigger, but don’t know what they’re going to do in life yet)
Region of maturation/differentiation
- Cells develop in specialization
Peocambium
A
Root-hair zone
- Another name for the region of maturation, where root hairs develop.
Root hairs
Extended growth of epidermal cells (trichomes) to increase root surface area and increase soil contact for absorption of water and nutrients
Cortex
- Largest region of the root, composed of parenchyma
* Function: storage, some support, transport (movement can go around or through the cells)
Endodermis
- Function: acts as a filter for incoming materials
* Contains the Casparian strip; is a tube all the way down the root
Casparian strip
- Like the “caulk” of the endodermis, between the cells to force materials to either enter the vascular tissue through the cells, or be blocked from entrance
- Function: seals the endodermal layer, filters materials
Passage cells
- At the ends of “arms” of xylem. Small, thin-walled gaps in the endodermis.
- Function: to help channel water directly to the xylem and help prevent it entering the phloem.
Vascular cylinder
- The core of tissues inside the endodermis.
Pericycle
- Thin layer of meristematic cells inside the endodermis, usually one cell wide.
- Function: makes new cells, can result in side (lateral) roots, and parts of the vascular cambium in dicots come from the pericycle.
Food-storage roots
Roots are enlarged to store large quantities of starch and other carbohydrates. Ex: sweet potatoes and yams, and dandelions.
Water-storage roots
Store water, in arid areas
Propagative roots
Ex: make stem cells turn into root cells in cuttings. Some plants produce them naturally, when send out suckers via the roots. They begin a new plant.
Pneumatophores
- Root extensions above the soil surface. Found usually in tropical/swamp species where the soil can be saturated.
- Function: Aid in oxygen and other gas exchange.
Aerial (“prop”) roots
- Roots originating above the surface of the soil. Vines produce these, that climb houses and trees. Corn grows prop roots to help stabilize the plant in wind.
- Function: support
Contractile roots
Pull the plant deeper into the soil until stable soil temperature is found.
Buttress roots
Tall, narrow “feet” that merge in appearance with the trunk. Gives great stability.
Parasitic roots/plants
Feed off something else due to an inability to produce what it needs for itself. Example: dodder, a yellow plant lacking in chlorophyll, so takes nutrients from other plants
Adventitious Roots
Roots that arise/grow from an unexpected location, such as propagation roots and aerial roots
Mycorrhizae
A symbiotic relationship between specific fungus and plant roots where the mycelium join the root system. Fungus gives plant nutrients it can’t absorb as well by itself; plant gives fungus sugars it can’t synthesize.
Root nodules
Joining of bacteria to roots; fixes nitrogen (legumes).
Roots
- 2 forms: tap root, fibrous root system
- Functions: anchor the plant, absorb water and nutrients, transport materials (water, nutrients, sugar and starches), storage (but not annuals), growth
- Majority are in top 18” of soil; do extend beyond the drip line.
- New roots at ends do most of the absorbing; older roots are for storage and support.
Tap root
Better for stability; reaches further down into the ground for minerals and water
Fibrous root system
Better for erosion control. Redwoods have this, but intertwine with other trees’ roots to form a stable mat.
Layers of the root
1) Epidermis
2) Cortex
3) Endodermis
4) Pericycle
5) Vascular tissue/cylinder
Epidermis
Protection against organisms in the soil, temperature, absorption of water and nutrients, produce root hairs (trichomes)
2 plant types
1) Monocotyledons (monocots)
2) Dicotyledons (dicots)
Monocotyledons/monocots
- In grass family (grains, corn, etc.).
- Has one cotyledon (storage part of the seed)
- Vessel cell (xylem) arrangement in vascular cylinder is circular.
Dicotyledons/dicots
- Has 2 cotyledons in storage part of the seed.
- Think: peanuts with 2 halves, beans, walnuts.
- Vessel cell (xylem) arrangement in vascular cylinder has “arms”; many form an “X” with xylem
Fungus
2 main parts:
1) Mushroom - reproductive structure to produce spores
2) Hyphae (singular)/Mycelium (plural) - thread-like structure that breaks down organic matter and absorbs nutrients vie enzymes; usually living in the soil
